Posted
by
samzenpus
on Monday November 19, 2012 @10:20AM
from the check-me dept.

sciencewatcher writes "A 1999 cold case rape and murder in The Netherlands has been solved. Dutch police asked 8000+ men living within 5 kilometers of the crime scene to volunteer their DNA so that the murderer could be traced through (close or distant) family members sharing part of this DNA. As it turned out, the man now in custody turned in his own DNA, resulting in a 100% match. The request of the police was discussed here on Slashdot in September. The percentage of people participating was closing in on 90%; in the midsize town of the victim it was 96%."

Well, turning yourself in is admitting guilt and is psychologically hard.
This way, he is not directly admitting guilt (he does the same thing 90% of people in the neighborhood are doing), and there's a chance they won't get him, so it probably is much easier to (effectively) turn oneself in this this way.

If 96% of people had done it the social pressure might have been insurmountable.
He might have figured if he was the only person in the village who didn't give DNA the police would investigate him and find him anyway, so he might as well give the DNA, hope that there would be a mistake, or hope that he could claim "If it was me, then why did I give them my DNA?"

The guy had a wife and child. If your wife starts saying "Hey you should do this" it's probably hard to say no to her, even if you know it'll result in doom. After all, if you aren't the type who normally cares about or talks about civil liberties it's probably hard to come up with a negative response that doesn't sound fishy as hell.

In Sweden we have the PKU-registry. Anyone born after 1975 has a DNA sample taken from them at birth, however it can only be used for your own treatment, identification of remains or research. So far they have kept their part of the promise of not letting it be used for criminal prosecution. Even tho as some would like it to be included in tools available for the police.

I don't know about their government but what I do know is that our government would store that DNA data forever. Not only that but they would share this DNA data with anyone, possibly including Insurance companies, and private corporations. Finally the last straw is that even if they don't just give the data away they will not take any consideration to secure the data.

There really ins't a better way. DNA really is our only answer to the issue of Justice in relation to sever crimes like Rape and Murder. People are falsely accused of Rape and Murder all the time, and occasionally we find out about it. Hopefully before we put them to death or destroy their lives. The end goal it to make it so that you cant do those things without getting caught. It's got to the point were Rapists have been doing things to reduce the chance of their DNA being present. Which also reduced the odds that a Rape would result in a child since I don't know of any way of a child being conceived without leaving some DNA behind. If you believe that Rapists are a result of bad genetics taking advantage of sexual reproduction to gain a marginal reproductive advantage then they are weeding themselves out. Ether they use protection to avoid detection, or they don't and they get caught. That along with free morning after pills for rape victims and you'll see a drastic decline in the people willing to Rape others. Murder is a bit different but if we get to the point where premeditated murder is unheard of, and are left only with crimes of passion then I'll be satisfied with the results. As bad as Rape and Murder is punishing Innocent people is much worse. DNA alone shouldn't convict, but it is a very good start. You're argument of "There's got to be a better way to solve these rapes than asking all of us to give up private information at the threat of arrest." is also a Red Herring. No one in the article was threatened with prison time for not volunteering their DNA. If you're stupid enough to commit a crime, and then submit your DNA voluntarily to be checked against said crime You're a Moron and deserve the Darwin Award. What they were hoping for was a Parent, Child or Grandchild to donate their DNA to help narrow down the list of possible suspects. Their was always the possibility that the suspect was already dead, or not stupid enough to submit his own DNA.

Those "DNA matches" are not. AFAIK, what's matched a very tiny amount of information from the DNA. I figure there may be a reasonable probability that when you've got so many volunteers, there will be a "100%" match. I don't know what kind of "matching" they are using, of course, so feel free to correct me if I'm totally off-base.

I find this method seriously scary due to the probability of a false positive. I mean, suppose you have a system that only fails once in a million times and the killer has already left the country. You ask the two million people in the metropolitan area to submit DNA. You get on average two matches. One doesn't have an alibi. You take him to trial and tell the jury that he not only doesn't have an alibi, he had a 1 in a million DNA match. It sounds pretty convincing. It is very possible the jury won't have the understanding of statistics to ask "was this a sweep or did you only test a couple of likely suspects?" Nor is it likely that the information will be volunteered by the court.

In a room of about 20 people you have a 50/50 chance of having the same birthday as someone else in the room. What they're doing here is taking one sample and comparing it to hundreds or thousands of men.

I've been lead to believe that birthday paradox also applies to DNA too... So if you take a sample size of thousands or so presumably unrelated people you might find people who match in such a way that it would be acceptable evidence in a court of law.

Someone smarter than me can do the math but 1:1,000,000 chance vs 3,000 Samples... How many are likely to come up close enough to prosecute?

A confession should not be the end of the story. An instructive case in the news these days is the story of Sture Bergwall, better known under his serial killer name Thomas Quick. It turns out he likely didn't kill a single person - he was just a disturbed drug addict who made up stories (mostly under the influence of strong sedatives and "repressed memory therapy") to fit unsolved cases. They glossed over his inaccuracies, contradictions and the total lack of evidence in case after case, year after year.

(An interesting bit is that Bergwall's defender was the lawyer/politician Claes Borgstöm, who's currently infamous for pursuing Julian Assange. If he had done any due dilligence at all, he must have suspected something was amiss. You got to wonder if there was something in his ideology which caused that gross failure.)

A lot of people, who aren't so smart and are aware of it, tend to be totally dominated by supposedly scienfific authorities. If the authority says it's absolutely certain you did it, they would rather doubt their own recall than the authority.

They don't do a "full scan", the marker matches is it. Crime scene samples are contaminated anyway so you aren't getting a "full scan" out of it in the first place.

In the case of "we suspect X due to this evidence, test his DNS for a match" then a match to enough markers would be very good evidence - it's very unlikely he would match by chance. But doing it the other way "compare all these samples against this one" gives you a much higher chance of a random match. 8000 isn't that high a number though - assuming they had a lot of markers. It's still a terrible way to use DNA evidence - and you can be pretty sure they won't tell the jury about the actual odds of a random match in a multi-sample comparison and instead just use the 1:1 match odds.

It's interesting to see this guy come forward, you can google dna testing and figure out what's going on. If he was indeed the killer he could've voluntarily declined, like I'm sure some people did.

People did, both in this test, and the previous test. I don't think they've mentioned whether this suspect had also had a DNA sample taken the first time around.

Here's the thing about this second set of tests. They weren't specifically looking for a direct match with the perp (though that ending up being the case is, I'm sure, a boon) but rather for a match to a family member of the perp.

So assume the first time around he declined to let a DNA sample be taken, and gets to walk scott free.

But this second time around, his sons who actually knew the victim at the time, may or may not be tested against. Being the father of them, he could either take that risk and hope they did not get tested against... or also supply a sample to spare his sons the additional shame, guilt, etc. of effectively having ousted their very own father by virtue of the lab having a direct match.

That would be my guess as to any reason for coming forward, at least. Who knows, maybe he just started feeling guilty, grew a conscience, etc. and the above is unrelated.